Nonwoven fabrics are conventionally manufactured from webs of staple fibers which are provided, through various bonding techniques, with structural integrity and desired fabric characteristics. Fluid entangling techniques in which nonwoven webs are mechanically bonded by application of dynamic fluid forces to web materials are among the most widely utilized processes for manufacturing nonwoven fabrics.
Conventional nonwoven process lines employ carding apparatus to process staple fibers for use in nonwoven fabrics. In the carding process staple fibers are opened, aligned, and formed into a continuous web free of impurities. An exemplary carding apparatus is illustrated in U.S. Pat. No. 3,768,118 to Ruffo et al.
Following carding operations, the processed fiber webs are treated with high pressure columnar fluid jets while supported on apertured patterning screens. Typically, the patterning screen is provided on a drum or continuous planar conveyor which traverses pressurized fluid jets to entangle the web into cohesive ordered fiber groups and configurations corresponding to void areas in the patterning screen. Entanglement is effected by action of the fluid jets which cause fibers in the web to migrate to void areas in the screen, entangle and intertwine.
Prior art hydroentangling processes for producing patterned nonwoven fabrics which employ high pressure columnar jet streams are represented by U.S. Pat. Nos. 3,485,706 and 3,498,874, respectively, to Evans and Evans et al., U.S. Pat. No. 3,485,708 to J. W. Ballou et al., and U.S. Pat. No. 2,862,251 to F. Kalwaites.
The art has recognized that fiber orientation within nonwoven web materials employed in fluid entangling processes correlates to physical properties in the bonded and processed nonwoven fabrics. Fibers in carded webs are characterized by machine direction ("MD") and cross-direction ("CD") web axes. MD and CD fiber orientations respectively refer to orientation in the process and cross directions on nonwoven process lines. Carded webs have a predominance of MD fibers which yield fabrics having correspondingly enhanced MD and diminished CD tensile strength.
To provide uniform tensile strength characteristics in nonwoven fabrics, the art has introduced techniques which randomize web fibers prior to bonding. For example, it is known in the art to employ airlay systems to randomize carded web materials. Such systems typically include disperser mechanisms which disperse fibers from a mat composed of fibers into a turbulent air stream for randomization and collection on web forming screens. Exemplary airlay systems are shown in U.S. Pat. No. 3,900,921 to Zafiroglu and U.S. Pat. No. 4,089,086 to Contractor et al.
Another technique employed in the art to "randomize" web fibers includes the use of "randomizing rollers" and doffing mechanisms in carding operations.
From the foregoing, it will be appreciated that prior art techniques for enhancement of tensile strength in nonwoven materials have been directed to pre-entanglement web processing. The present invention is directed to a fluid entangling process and related apparatus which obtains a higher degree of fiber entanglement with consequent improved fabric texture and tensile characteristics. An entangling support member is provided for use in a conventional process line which generates patterned concentrations of energy flux to enhance fiber entanglement. Advantageously, the apparatus of the invention can be integrated with conventional nonwoven production lines without requirement of extensive and costly retooling.
It is a broad object of the invention to provide an improved nonwoven fabric having textile-like aesthetics and tensile strength features which advance the art.
A more specific object of the invention is to provide an improved hydroentangling process which yields a durable, nonwoven fabric which is characterized by conformability to wiping surfaces, supple drape, dimensional stability, and textile-like qualities.
A still further object of the invention is to provide an apparatus and process for production of nonwoven fabrics which obtain improved production line efficiencies and process speeds.